477 S U S T A I N A B L E R E T R O F I T T I N G O F E X I S T I N G A N D H I S T O R I C B U I L D I N G S Marina Traykova Assoc. Prof., PhD, University of Architecture, Civil Engineering and Geodesy, Bulgaria, Sofia 1046, 1Hristo Smirnenski Blvd., e-mail marina5261@abv.bg Tanya Chardakova Phd Student, University of Architecture, Civil Engineering and Geodesy, Bulgaria, Sofia 1046, 1Hristo Smirnenski Blvd., e-mail tanq_chardakova@abv.bg A B S T R A C T In this paper, the philosophy of life cycle sustainability assessment of buildings, with respect to some important codes and standards, is first addressed. Then some special considerations for its application on existing and historic buildings are analyzed. Finally, some general conclusions concerning the sustainable retrofitting of existing and historic buildings are given. Keywords: life cycle sustainability assessment, retrofitting I N T R O D U C T I O N The development of human civilization through the centuries, and especially the industrial age, has led to a ever-growing increase of human population, consumption of resources and waste output per person. Thus, in the last decades, the environmental impact of human kind has become so obvious, that the need of immediate actions to limit it can be no longer denied. The answer to this process is sustainability, or the responsibility to maintain and care for the natural and physical environment. Construction and operation of buildings have a main contribution to the environmental impact. For example, according to [1], in the United States building operations alone contribute over 38% of the country's carbon dioxide, 12% of the water consumption and 40% of the energy use. Waste from demolition, construction and remodelling makes up more than 35% of all the non-industrial waste. Construction and remodelling of buildings account for 40% of raw material use globally each year. These striking numbers show that the question of sustainability of buildings is of the upmost importance and there is urgent need for its implementation in the acting codes and standards. While the first steps in this direction have been already made, the existing standards mainly address new buildings. Codes and other documents, concerning the sustainability of existing and/or historic buildings specifically, however, are scarce.